I agree with WOW on Ginobili, unpredictable is a pretty accurate description of his style, although you do have to take the bad with the good in his case, he has too much upside for his unpredictability to be factor in whether he is valuable to a team, he is, just not top tier by any stretch of the imagination. I would say between 2nd and 3rd tier, he is not a game breaker nor is he unstoppable, he would never be a franchise player nor a player to build a team around, just a solid role player who hustles his behind off, nothing more.
I agree with Lurker on Marbury and Iverson being unpredictable but not on Iverson being unstoppable, scoring points while your team doesn't make the playoffs or is at best a 1st round and out in a weak EC doesn't put you in the rarified unstoppable category, we'll see how he does in Denver.
Arenas is rapidly becoming unstoppable simply because, like Kobe, Duncan, perhaps Wade, but particularly Kobe, he can kill you from anywhere on the floor, come to think of it, so can Dirk Nowitski, which makes him likewise unstoppable.